Faculty of Technology and Metallurgy
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Item type:Publication, The Analysis of The Cost of Dealing With Fabric Faults During Lays Spreading(2008)G. Demboski, M. Nofitoska - Some of the metrics are blocked by yourconsent settings
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Item type:Publication, Influence of Fabric Structure on Seam Slippage of Woll and Woll/Polyester Blended Fabrics(2006)16. G. Demboski, M. A. Carvalho, M. Nofitoska, D. Obadic - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A study of the morphological aspects of the indium electrorefining process(Serbian Chemical Society, 2001-12)Svetomir Hadži Jordanov, Aleksandar Dimitrov, Perica Paunović and Dragan SlavkovThe cathodic deposition of In was performed under conditions suitable for electrorefining purposes. The main goal of the study was: i) to determine the possibilities for In ultrapurification through multiple electrorefining with controlled parameters and ii) to study the regularities of the morphology of the In deposit as influenced by the electrodeposition conditions. Without application of special high purity techniques, it was possible to obtain an In purity level of 99.997 %, by repeating the refining procedure in a set of modular electrolysis cells with forced electrolyte circulation and applying modified current regimes. Irregular (non planparallel) migration of indium from the anode to the cathode and vice versa, as well as dendrite formation at the edges of the electrode prevented further repetition necessary for the achievment of higher purification levels. This provoked the need to study the morphology of the In-deposits. The phenomena and some regularities of In nucleation and grain growth, as influenced by the applied overpotential and quantity of current passed through the cell, were studied. Electrodeposition was performed onto a stationary Pt-electrode from amixed sulfate–chloride solution.SEMwith magnification up to 1000 was used to identify the morphology of the deposits. Granular grains were dominant at overpotentials of 85 and 110 mV, while at 160 and 185 mV, needle-like and nonbranched dendrites were visible. The deposit became less compact as its thickness advanced. The apparent thickness of the In layer increased from 20–25 to 320–380 m when the amount of charge was increased from 1 to 10 mA h cm-2. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A case history of hazardous waste formed in a chemical plant accident(Balkan Environmental Association (B.EN.A.), 2002-01)S.Hadzi Jordanov, P.Paunovic, D. Slavkov and A. DimitrovHazardous waste composed of a mixture of chemical products, such as partially burned and/or degraded products – all additives for civil engineering chemistry purposes, and pieces of production hall destroyed in the explosion, different in size and composition, estimated to a total amount of ca. 250 tones was disposed in a nearby mine field for cement industry. Unfortunately, the expectated soon permanent solution failed and, instead of planed 3 to 6 months, it took more than 10 years before further step was realized. During these 10 years a lot of efforts were done aimed to provide a proper solution that will meet the existing legal, environmental, and other regulations. Due to lack of experience, limited finances and other organizational inconcistences, all of the efforts were unsuccessfull. Finally, a solution was found in dislocation of the provisory landfill to an adjacent but already exhausted mine location as the most suitable solution, approved by government authorities as well. For this purpose a three compartment concrete shell (each compartment of ca. 5.5 by 5.5 meters and high 3 meters) was designed, constructed and made watertight. The waste was transferred to the new disposal location, poured out in the shells, compacted and finally covered with an appropriate concrete plate, thus forming a kind of encapsulated sarcophagi. Thorough precaution measures in manipulation were planed and applied in order to prevent any further accident. First of all the existing cell was carefully opened (by drilling a hole) and checked for eventual emission of dangerous (flammable, explosive, poisonous, etc.) gases or vapors. When this possibility was eliminated, the cell was completely opened and samples for physico-chemical testing were picked up. 14 distinguishable samples were taken from the same number of different materials. All samples were tested in the laboratory for leaching in water, change of color, pH and electrical conductivity of the leachate, and organoleptic changes in solid leaching residues. 5 out of these 14 samples were found to give leachate with changes that indicate possible contamination of soil, underground water etc. This finding was a base for the decision that the waste could not be disposed in an open landfill and exposed to interaction with atmospheric precipitations, leading to an eventual environmental threatening. The need for constructing a special disposal cell (as described above) arose from these circumstances, no matter that its price was not at all neglectable. Manipulation with the landfill content, as well its transportation (together with a lot of soil-material) to the new landfill was done carefully and without any spilling. Measures for monitoring any leakage or other possible pollution from the described sarcophagi are planed, no mater that in its content inert soil material or harmless waste are the dominant part. One should be stressed out that this is the very first experience in Macedonia with treatment and legal disposal of hazardous waste. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Corrosion behaviour of steel and copper as influenced by local atmospheric conditions(Balkan Environmental Association (B.EN.A.), 2004-01)S. Hadzi Jordanov, D. Slavkov, A. Dimitrov, P. PaunovicCorrosion of steel (0147, JUS) and copper (99,99%) was studied during past 18 years in a network of 8 testing sites situated in locations of R. of Macedonia with typical microclimate. Climate conditions were registered simultaneously, in order to establish their effect on the observed phenomena. Weight loss, as well as increase of electrical resistance and time of wetness were periodically registered. Testing in a climate chamber was also performed in order to elucidate the individual effect of the most significant parameters. It was found that the corrosion rate depends strongly on the: atmospheric pollution, humidity and temperature, as well as on the time of wetness of metallic surface; thickness and compactness of accumulated corrosion products; composition and morphology of primary corrosion products; orientation of the corroding metal surface, etc. A model based on the sequentional nature of the corrosion of metals in atmosphere was developed, based on the measured pattern of time-of-wetness and precise insight in the discrete progress of the corrosion process. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Electrocatalysts in the last 30 years - from precious metals to cheaper but sophisticated complex systems(Society of Chemists and Technologists of Macedonia, 2004-11)Svetomir Hadži Jordanov, Perica Paunović, Orce Popovski, Aleksandar Dimitrov, Dragan SlavkovThe paper is concerned with the advance and diversification of materials used as electrodes for evolution of chlorine, hydrogen and oxygen. In the first part a survey is given of our research in the field of electrocatalysis 30 years ago, when Ru and other precious metals were the exclusive electrocatalyst materials. A brief scope of the achievements of electrocatalysis in that period is given as well. The second part deals with our recent research on formulation and characterization of a new class of electrocatalysts, based on a combination of non-precious metals, but still exhibiting an ability to promote hydrogen evolution reaction as successful as platinum and other precious metals are. Among the produced (non-platinum) catalysts the best performance for the hydrogen evolution reaction was measured at the electrocatalyst containing Co or CoNi as hyper d phase and TiO2 as hypo d phase. A typical formulation of the electrodes is, e.g.: 18% (TiO2) alloyed with 10% Co and applied on a substrat of carbon powder (Vulcan XC-72). At this electrocatalyst hydrogen evolution overpotential at 10 mA·cm–2 was 40 mV higher than that on a corresponding electrode containing platinum as hyper d phase. For both electrocatalyst systems of interest analysis is made and aimed to recognize the sources that cause the electrocatalytic activity. This is the proper way how to use the acquired knowledge for further improvement of the existing materials or/and to discover new ones.
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